Amp-Up Your Search Strategies with “Synonym Sets”

In my last post, I discussed how to identify the search terms in a query. But each of those terms represents only one way of expressing the underlying concept. There are often multiple ways of referring to the same concept. For example, think of the concept of “car.” Some may refer to this as “auto,” or “automobile,” or “motor vehicle,” or “convertible,” or “SUV.” The same applies to search concepts in a scientific query. Since there are often many ways of referring to the same scientific/medical concept, it will be critical to include these “synonyms” in your search string in order to capture all the literature about your topic.

Let’s take the search query we’ve been working with, “What are the safety issues around using VEGF inhibitors for neovascular age-related macular degeneration?” As we’ve discussed, the main search concepts are:

1. Safety
2. VEGF inhibitors
3. Neovascular age-related macular degeneration

?Safety

?There are numerous terms that represent the concept of “safety” in medical articles (e.g. adverse event, side effect, unwanted outcome, etc). When monitoring the literature for safety issues, it is essential to create an exhaustive list of these in order to ferret out all of the evidence in the literature.

?VEGF Inhibitors

When it comes to acronyms, the first step is to define the phrase the acronym stands for. In this case, VEGF is an abbreviation for “vascular endothelial growth factors.” It’s usually easy to find abbreviation definitions by googling “define VEGF,” or by checking it in MeSH. In MeSH you can also find “entry terms” (i.e. closely related terms to the “preferred” term) that may often be used in the literature about the topic. A great source to build your list of synonyms!

In this case, don’t forget to “AND” these terms/phrases with “inhibitors” or you will get the opposite of what you seek in your results!

?Neovascular Age-Related Macular Degeneration

Neovascular age-related macular degeneration (Wow! That’s a mouthful!) is often abbreviated to “nAMD” or “wAMD” (i.e. wet AMD). In addition to using all the synonyms you can find in MeSH for this concept, it will also be important to include any abbreviations for the condition, as abbreviations abound in the literature.

Here are some tips for gathering synonymous terms that will give you confidence that you’re capturing most of the literature:

1. Look up your terms in the MeSH index and also refer to the “Entry Terms” at the bottom of each record.
2. Talk with a subject matter expert (SME) to elicit known synonyms.
3. Read some reviews about your topic to pull terms from overviews.
4. If you have access, look up your terms in Embase’s Emtree (Embase’s index) and refer to the synonyms listed under the “Term Information” for each record.
5. In the case of safety terms, Embase’s “PV Wizard” is also a fantastic resource for a comprehensive list of basic safety terms.

Here’s are some example synonym sets for our terms:

Safety:

• “Safety”[Mesh]
• Adverse event
• Complication
• Side effects
• Eye redness
• Floaters
• Blurry vision
• Detached retina

VEGF inhibitors:

• “Vascular Endothelial Growth Factors”[Mesh] AND inhibitors
• VEGFs AND inhibitors
• Anti-VEGF treatments

Neovascular age-related macular degeneration:

• “Macular Degeneration”[Mesh] AND wet OR neovascular
• Maculopathy AND wet OR neovascular
• Neovascular age-related macular degeneration
• Wet age-related macular degeneration
• nAMD
• wAMD

But lists will only get you so far with your search strategy! Next, we’ll discuss how to map these synonyms into search strings, and how to combine search strings into search strategies to bring back laser-focused results.